i) Field of the Invention
The present invention relates to a dicing method of a semiconductor wafer for use in producing semiconductor devices such as a rectifier diode or the like, and more particularly to a semiconductor dicing method in which a semiconductor wafer having at least one surface plated with a metallic material abundant in malleability and ductility is cut by moving the wafer relative to a rotating blade.
ii) Description of the Related Arts
Conventionally, a semiconductor dicing method in which a semiconductor wafer having at least one surface plated with a metallic material abundant in malleability and ductility is cut by moving the wafer relative to a rotating blade. In this semiconductor dicing method, as shown in FIG. 1, a semiconductor wafer 2 plated with Ag (silver) is mounted on a PVC (polyvinyl chloride) tape 5 provided between frames 4 and a rotating blade 1 is moved relative to the semiconductor wafer 2 at a certain feeding speed to cut: the semiconductor wafer 2 into pellets. For example, the cutting position of the semiconductor wafer 2 is shown in FIG. 2 and the semiconductor wafer 2 is cut at a central position of a groove etched on the semiconductor wafer 2. A glass layer 21 is provided over the groove. The glass layer 21 prevents surface leakage of P and N layers of the semiconductor wafer 2. The semiconductor wafer 2 plated with silver layers 22 and 23 is cooled down by cooling water immediately after the cutting. This cooling water is supplied at the rate of 1.4 liter/min.
An adhesive is coated on the upper surface of the PVC tape 5 to provide convenience for fixing on the desired position and preventing the scattering of the pellets after cutting. In this case, the revolving speed of the blade 1 while cutting is between 3.times.10.sup.4 and 6.times.10.sup.4 r.p.m. and the blade feeding speed is set constant in the range of 30 to 60 mm/sec.
Incidentally, in a plating method of the semiconductor wafer such as a jet plating method, a plating apparatus has a construction shown in FIG. 3 and the semiconductor wafer 2 is placed on a negative electrode in the upper position, as shown in FIG. 3. In this case, a plating liquid flow passes by the periphery of the semiconductor wafer 2 and thus, as shown in FIG. 4(a), a thickness of a silver plating 3 near the external peripheral portion of the semiconductor wafer 2 is 7 to 13 .mu.m which is thicker than the thickness (6 .mu.m) of the central portion.
Since the silver is abundant in malleability and ductility, in the thick portion of the silver plating, that is, the external peripheral portion, the silver once cut is fused again by the heat of the rotating cutter, and hence the semiconductor wafer 2 can not be separated into individual pellets. Further, in the glass layer 21, when cutting at the higher feeding speed of 30 to 60 mm/sec, an impact force given to the glass layer 21 is strong, and causes cracks or chipping in the glass layer 21. As a result, generally, the semiconductor wafer 2 can not be used as products or goods.
In order to solve the above problem, it is considered that the feeding speed of the blade 1 is reduced to at most 20 mm/sec and the semiconductor wafer is sufficiently cooled by the cooling water to suppress the heat generation. However, the reduction of the blade feeding speed brings about a sharp reduction in production amount.